Typically, in a transportation device such as an automobile or a motorcycle, a suspension apparatus is interposed between a vehicle body and a vehicle wheel in order to suppress transmission of an impact generated by irregularities on a road surface or the like to the vehicle body.
JP2011-117493A, for example, discloses a front fork that suspends a front wheel of a motorcycle. The front fork includes a suspension apparatus main body constituted by an outer tube connected to a vehicle body side and an inner tube coupled to a vehicle wheel side and inserted retractably into the outer tube. A shock absorber and a suspension spring are housed in parallel inside the suspension apparatus main body.
The shock absorber includes a pair of chambers defined by a piston within a cylinder, a flow passage formed in the piston to connect the pair of chambers in the cylinder, and damping force generating means for applying resistance to a working fluid passing through the flow passage. The shock absorber includes a bypass passage that connects the pair of chambers in the cylinder so as to bypass the flow passage in which the damping force generating means is provided, a variable throttle member that is inserted into the bypass passage to be capable of advancing and retreating in order to modify an opening of the bypass passage, and an actuator that drives the variable throttle member.